Chris Brown Jail Is TerribleI Feel Like a 'Caged Animal'

3/21/2014 10:23 AM PDT

Chris Brown -- Jail Is Terrible ... I Feel Like a 'Caged Animal'

You'd think the photos of Rihanna's battered face would have left an impression ... on him. But apparently it took a few days in solitary to shake Chris to the core.

One source -- who recently spoke with Brown on the phone -- tells us, Chris says he feels like "a caged animal," calling it "the worst experience of my life."

We're told Chris has been spending his time behind bars working out and writing music. He's telling people on the phone, "I'll never f*** up again."

Not particularly convincing.

Lucky for Chris ... he's rich enough to buy his way out of jail -- as we reported, he's negotiating to pay offhis alleged assault victim in D.C. so the case goes away and the judge in the Rihanna case lets him loose ... to roam freely again.